Preheat oven to 350ºF. In a medium skillet, heat oil over medium-high heat. Sauté celery, onion and poblano pepper until onion is translucent, 5 minutes. Mix in carrot and garlic, and cook until vegetables are soft, 3 minutes. Set vegetables aside to cool.

Meanwhile, tear bread into 1-inch pieces. Whirl bread in a food processor, pulsing until the texture of crumbs. Set the breadcrumbs aside.